Optical Transceiver FPC Layout for Low-Loss DSP Module Links
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Solution Overview
Problem
Existing optical transceivers face challenges in achieving ultra-high speed operation due to high-frequency loss and heat dissipation issues, particularly in high-bandwidth coherent driver modulators and receivers, where the connection configurations between digital signal processors (DSP) and optical modules are not optimized, leading to impedance mismatching and divided heat dissipation paths.
Innovation Solution
The optical transceiver design incorporates a flexible printed circuit (FPC) connecting the DSP and optical modules with a differential high-frequency line, featuring a phase difference adjustment bend to minimize phase differences and a unified heat dissipation mechanism, aligning heat generation components to facilitate upward heat dissipation, and eliminating high-frequency paths through vias and ball grid arrays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a surface mount (SMT) type package with via structure is used to mount optical modules on PCB, then mountability is improved, but high-frequency transmission characteristics deteriorate due to via structure and impedance mismatching
Solution Approach 1:
The patent extracts and eliminates the via structure from the high-frequency signal path by using a land pattern configuration that allows direct mounting of the optical module without requiring vias to pass signals through the PCB. This removes the source of high-frequency loss and impedance mismatching while maintaining ease of manufacture through standard surface mount techniques.
Solution Approach 2:
Instead of passing high-frequency signals through vias in the conventional SMT approach, the patent inverts the connection method by using a land pattern that enables direct electrical connection between the optical module and PCB trace, eliminating the via structure from the signal path while maintaining mountability.
2Ease of manufacture
If DSP, transmission module, and reception module are mounted in separate packages on PCB, then ease of manufacture is improved, but propagation loss increases limiting speed improvement
Solution Approach 1:
The patent merges the DSP, transmission module, and reception module into a single integrated package structure. This co-packaging approach eliminates multiple separate PCB connections and reduces propagation loss by keeping high-frequency signal paths short and contained within the package, while still maintaining ease of manufacture through standardized package assembly processes.
3Temperature
If optical modulator chip is mounted on Peltier element for temperature control, then temperature stability is improved, but power consumption increases and thermal runaway risk occurs due to heat inflow from nearby DSP
Solution Approach 1:
The patent introduces a heat shield or thermal isolation structure as an intermediary between the DSP and the optical modulator chip/Peltier element. This mediator blocks heat flow from the high-power DSP to the temperature-sensitive optical components, reducing the cooling load on the Peltier element and thereby lowering power consumption and eliminating thermal runaway risk while maintaining temperature stability.
4Loss of energy
If co-package structure with DSP and optical modules is used, then propagation loss is reduced, but mounting process complexity increases and heat dissipation becomes problematic
Solution Approach 1:
The patent segments the co-package structure into modular functional units (DSP module, optical module, heat dissipation module) that can be independently manufactured and then assembled using standardized processes. This segmentation reduces mounting process complexity while maintaining the propagation loss benefits of the integrated structure, and separates heat dissipation management into its own module.
Data Source
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AI summary
To present a configuration of a smooth high-frequency connection between a DSP and an optical module in an optical transceiver and to provide an optical transceiver capable of operating at an ultra-high speed. An optical transceiver according to the present disclosure includes: at least one optical module that is mounted on a PCB; a DSP that is mounted on the PCB; an FPC that connects the DSP and the optical module or the PCB and the optical module; and a differential high-frequency line that is configured such that a p-side line and an n-side line form a differential pair, and is formed such that a signal propagates inside a DSP substrate of the DSP, inside the optical module, and between the DSP and the optical module, wherein the differential high-frequency line disposed between the DSP and the optical module has at least one first bent portion.